The National Transportation Safety Board today determined that the probable cause of the crash of an Air Tahoma cargo airplane, on August 13, 2004, was "fuel starvation resulting from the captain's decision not to follow approved fuel crossfeed procedures." Contributing to the accident were "the captain's inadequate preflight planning, his subsequent distraction during the flight, and his late initiation of the in-range checklist." Further contributing to the accident, the Board said, was "the flight crew's failure to monitor the fuel gauges and to recognize that the airplane's changing handling characteristics were caused by fuel imbalance."
"Here again we see the tragedy that can result when time- tested procedures are not respected," said NTSB Acting Chairman Mark V. Rosenker. "The accident also points up the severe consequences that can follow when the operator of an aircraft, or any other vehicle, becomes distracted."
The accident airplane, a Convair 580, was operating as a DHL Express cargo flight from Memphis TN, when it crashed on approach to landing at Cincinnati/Northern Kentucky International Airport, in Covington KY. The first officer was killed and the captain was injured. The airplane was destroyed by crash impact forces.
Examination of the wreckage revealed no evidence of any pre- crash problems with the airplane's engines, systems or structures. There were no indications that the airplane's cargo had shifted during the flight. Investigators also determined that there was sufficient fuel on board for the flight from Memphis to Covington.
Cockpit voice recorder information indicated that the captain began fuel crossfeed operations about 50 minutes into the flight, and that he allowed it to continue unmonitored for almost 30 minutes. Post-accident examination of the wreckage revealed that, contrary to approved procedures, the fuel tank shutoff valve had been left open during the crossfeed operations, which allowed fuel transfer from the left tank to the right tank.
The Board concluded that, during the airplane's descent to landing, the fuel in the left tank, which was providing fuel to both engines, was exhausted because both engine-driven fuel pumps drew air from the left tank into the fuel system instead of fuel from the right tank, which led to a dual engine flameout caused by fuel starvation. Consequently, the Board recommended that the FAA issue a flight standards information bulletin to familiarize Convair 580 operators with the circumstances of the Air Tahoma accident, including the importance of closing the fuel tank shutoff valve for the tank not being used during crossfeed operations. The Board further recommended that Convair 580 operators be required to use the same output pressure settings on their left and right fuel pumps.
The Board, noting that additional details about the flight crew's actions after the loss of engine power would have aided the investigation, reiterated a previous recommendation to the FAA (A-99-16), which called for retrofitting airplanes with independently powered cockpit voice recorders.
The texts of these recommendations and a synopsis of the report can be found on the NTSB web site at www.ntsb.gov. The complete report will be released at a later date.